1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a backlight unit having a light guide plate structure capable of preventing light leakage from a light source and a liquid crystal display device having the same.
2. Description of Related Art
Since liquid crystal display devices have the advantages of small size, light weight, and larger screen compared to cathode ray tubes, the development of liquid crystal display devices has been actively conducted, and the application range of the liquid crystal display devices has been rapidly spreading. Liquid crystal display devices are used in laptop computers, monitors for desktop computers, large display devices, and mobile communication devices.
Such a liquid crystal display device displays desired images by controlling the quantity of transmitted light according to image signals applied to a plurality of control switches arranged in a matrix form, and comprises an LCD panel on which images are directly displayed, an LCD driving circuit for operating the LCD panel, and a backlight unit used as a light source of the liquid crystal display device.
As small and medium sized liquid crystal display devices have been rapidly made thinner in recent years, a method of designing a light guide plate of a backlight unit so as to be at an inclination is frequently employed as a means of reducing the thickness of the backlight unit.
That is, one side serving as an incident portion of the light guide plate is formed thick corresponding to the minimum thickness of a light emitting diode (LED) used as a light source of the backlight unit, and a portion corresponding to an active area of the LCD panel is formed thinner than the one side serving as the incident portion of the light guide plate, considering the thickness of an optical sheet placed on the upper end.
At this point, a flexible printed circuit board for supporting an LED light source is supported by the light guide plate as its one end is adhered to an inclined surface of the light guide plate.
As such, the portion of the flexible printed circuit board adhered to the light guide plate is not a flat surface but an inclined surface. Thus, if the flexible printed circuit board having elastic force is adhered to the inclined surface of the light guide plate while being bent, the flexible printed circuit board may come off the inclined surface by its elastic force.
When the flexible printed circuit board comes off the inclined surface, there arises the problem of leakage of light generated from the LED light source through a space formed between the flexible printed circuit board and the inclined surface.
Meanwhile, the flexible printed circuit board is adhered to the light guide plate by an adhesive tape, and the adhesive tape is made of a transparent material and has a predetermined thickness. Thus, the liquid crystal display device according to the conventional art has the problem of light leakage because light coming from the LED light source can leak to an upper part of the light guide plate through the inside of the adhesive tape.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.